Method for stopping leaks in tanks



ited States METHOD FOR` STOPPING LEAKSV 1N TANKS Sterling Beckwith, LakeForest, Ill., assgnor, by mesne assignments, to Constock Liquid MethaneCorporation, a corporation of Delaware Application August 18, 1954,Serial No. 450,776

7 Claims. (Cl. 62-170) My invention relates to improvementsv in methodof stopping leaks in tanks and has for one object to provide aVconvenient and reliable method of stopping a leak in a tank wherein themetal outer wall is insulated from the contents of the tank by aninsulating lining of such character that a cold boiling liquid containedwithin the tank is kept by the insulation out of contact with the outertank wall or shell.

My invention is especially applicable to tanks adapted to contain suchcold boiling liquids as liquefied methane at atmospheric pressure whichat that pressure boil at approximately -258 F., a temperature which, ifthe steel tank wall. were subjected to it, might have a dele- 'teriouseffect on the steel tank wall.

The lining being porous, may be penetrated by the cold liquid under theeffect of hydrostatic pressure and capillary attraction but underordinary circumstances ambient heat penetrating through the steel tankwall will heat the lcapillary streams of the liquid so as to vaporizethem and either build up a pressure in the tank lining which willprevent further outward movement of the liquid and will normally expelliquid which has already penetrated the lining. It is even possible thatthe rate of vaporization in the absence of the building up of suicientpressure will be suflicient to vaporize the liquid as it approaches thetank wall before it reaches the steel shell so that the tank wall issubjected to ambient temperature on the outside and to the temperatureof the ga's only on the inside, the gas being of low specifictemperature and being heated by the ambient temperature lfrom the steelWall, will be unable to lower the temperature of the steel shell or wallto the danger point.

This effect prevails so long as the sole avenue of access of the liquidthrough the insulating lining toward the shell is the capillaries in thelining. If for any reason whatever, however, there is a breaking down ofthe insulating lining so that the liquid may progressively penetrate thelining and reach the steel shell, trouble immediately ensues. The metalitself may deteriorate under the effect of the cold and in any eventcondensation of ambient moisture in the outer air will present diilcultproblems which must be avoided.

Therefore, it is necessary to provide some method by which in the eventof any breakage or deterioration of the inner insulating lining, whichpermits or would permit the escape of the liquid through the insulatinglining to contact the shellwill be prevented.

Such treatment must come from the outside in through the shell wall whenthe tank is in use because the low temperature of the liquid itself andthe fact that air must not be allowed toenter the tank because anexplosive mixture would result makes it impossible without completelyemptying the tank and purging it of gas, to do any repair work on theinside. However, such repair is equally useful during construction asthe lining is being built up. Since such repair would avoid thenecessity of tearing out the lining for repair during construction.

Because of the intense cold of the liquid, if and when Ziil PatentedDec. 24, 1957 there is any such break down of the lining which permitsthe liquid as a cold liquid to reach the tank shell, imrnediately thetemperature of the shell will drop far be low ambient temperature andmoisture condensation and frost formation will occur at the point wherethe liquid has passed through the lining as a liquid and in liquid phasehas contacted the shell. Thus it is easy to determine the place at whichthe leak through insulating lining has developed. I propose that whensuch leak is located, a hole is drilled through the steel tank and aliquid be forced through the hole into the lining. Paratlin is asuitable liquid for that purpose. Hot paraffin forced through the holeinto the lining will distribute itself throughout that portion of thelining where the leak has occurred, being forced into the lining by highhydraulic pressure, it will congeal or harden and furnish a. permanentplug to ll the leak in the lining. The pressure at which the liquid isforced into the lining will, of course, be held below the pressure whichthe lining can safely support.

Parain, of course, is a poor conductor of heat and since paraflnsolidiiies at ambient temperatures, no temperature on the outside of thetank will cause it to melt and if sufficient pressure is provided andthe paraffin either in liquid form or even in solid form is forced intothe leak, it will plug the leak and the cold of the liquid where itcomes in contact with the paraffin will insure that the paraffin remainsin solid condition at the point at which it is forced by the hydraulicpressure on the outside. The hydraulic pressure will be sufficient tocause the paraffin even as it congeals and solidies to distribute itselfthrough the pores of the lining but when the hydraulic pressure iswithdrawn and the parain has solidified, the hydrostatic pressure lofthe liquid in the tank, it being remembered that the liquid is atatmospheric pressure, will be insufficient to disturb the paraffin plug.Experience has taught that the parafn plug under these conditions willfurnish an effective closure and permanent repair for a leak ordangerous weakness in the lining which might ultimately become a leak.

My invention is illustrated more or less diagrammatically in theaccompanying drawing wherein the ligure shows a section through a tankadapted to contain cold boiling liquid. l

Like parts are indicated by like characters throughout the drawings andspecification.

1 is a steel tank; 2 a floor; 3, an insulating lining for wall andfloor, just porous to the extent that the cold boiling liquid 4, forexample methane, may penetrate the lining and move under hydrostaticpressure through the capillary pores in the lining toward the wall anddoor of the steel tank.

The dotted lines S indicate the zone or area to which the liquid inliquid phase may penetrate in capillary streams toward the outer tankwall. The area between 5 and 3 is the area in which the liquid in liquidphase does not penetrate but this area is filled normally with liquid ingaseous phase and since the gas has been raised at least to boilingtemperature by the ambient air at zone 5 and is of relatively lowspecific heat, the heat penetrating from 1 through the lining towardzone 3 will raise the temperature of the gas to a point at which, whereit contacts the steel tank l, it will be unable to dangerously reducethe temperature of the steel. If for some reason or another a break inthe lining takes place 'that there will be a barrier interposed betweenthe liquid and the tank wall. This paraffin will spread about theopening 6 through the capillaries of the lining and a tight plug willthus be provided which will prevent further access of the liquid to theshell.

Paraflin is a convenient material to be used at the temperatures andunder the conditions involved, it will not be appreciably dissolved bythe cold liquid; it will be kept in solid form by the cold and havingonce been forced into position as a plug to ll the leak in theinsulating lining, it will remain as a plug and prevent further contactof the cold boiling liquid with the steel shell.

Other suitable materials might be used. Under some circumstances evenwater might be forced into the leak or any other liquid may be usedwhich can be introduced and pumped as a liquid, will flow to some extentas it solidies and will remain a solid under the effect of the lowtemperature of the cold boiling liquid.

Another material that might be used to plug the leak is carbon dioxide.Carbon dioxide gas freezes to a solid or Dry Ice at temperatures farabove the temperature of methane. If carbon dioxide is forced into thelining at the leak, it will penetrate the leak, resist outward flow ofthe cold boiling liquid, will readily penetrate the pores of the liningabout the leak and will congeal to form a plug filling the leak andlling the area in the porous lining around the leak.

In any event, once the plug has been formed, the hole in the lining willbe closed and an easy way to close it would be to screw in a plug inplace of the threaded pipe through which the plug-forming liquid oriluid entered the lining.

Another suitable way in which to insert the plug is, after a hole hasbeen made in the tank wall at the leak point, to thread the hole andscrew into the threaded hole a valve member which when open permits thesealing liquid to be forced into the lining. As the sealing liquidpenetrates the lining and congeals or sets, resistance to flow willincrease and flow will be stopped when the pressure in the liningapproaches the safe pressure which the lining itself can stand withoutrup- V ture. This pressure, of course, depends on the character of thelining and its resistance to internal pressure which in each case willbe determined empirically for any specific type of lining.

A suitable sealing liquid is a mixture of parain and turpentine which bycontrol of the relative proportions can be made to congeal at anydesired temperature in a wide range, such as from 220 F. to 100 F.

I claim:

1. The method of stopping from the outside a leak in the porousinsulating lining of a metal walled tank with a frozen plug of sealingfluid, which consists in making a hole in the metal wall, in line withthe leak and forcing into the lining, through the hole under hydraulicpressure, a sealing fluid the freezing point of which is above thetemperature of the liquid contents of the tank.

2. The method of stopping from the outside a leak in the porousinsulating lining of a metal walled tank with a frozen plug of sealingfluid, which consists in making a hole in the metal wall, in line withthe leak and forcing into the lining, through the hole under hydraulicpressure, a sealing Huid the freezing point of which 4 is above thetemperature of the liquid contents of the tank, and continuing theintroduction of the sealing liuid until it has congealed and formed aplug in the insulation, to close the leak.

3. The method of protecting the outer metallic shell of an interiorlylined tank from contact with a cold boiling liquid escaping through aleak in the lining with a frozen plug of sealing uid, which consists inmaking a hole in the shell in line with the leak and forcing into theleak and into the pores of the lining about the leak, through the holeunder hydraulic pressure, a sealing fluid, the freezing point of whichis above the temperature of the cold boiling liquid in the tank.

4. The method of protecting the outer metallic shell of an interiorlylined tank from contact with a cold boiling liquid escaping through aleak in the lining with a frozen plug of sealing fluid, which consistsin making a hole in the shell in line with the leak and forcing into theleak and into the pores of the lining about the leak, through the hole,under hydraulic pressure, a sealing fluid, the freezing point of whichis above the tempera ture of the cold boiling liquid in the tank, andcontinuing the introduction of the sealing fiuid until it has congealedand formed a plug in the insulation, to close the leak.

5. The method of stopping a leak in the porous insulating lining of ametallic walled tank from the outside which tank contains a cold boilingliquid, such for example as methane, which consists in making a hole inthe metal wall at the point where the leak has permitted the liquidmethane to contact and chill the tank wall, forcing into the liningthrough the hole under pressure a sealing gas, the freezing point ofwhich is above the temperature of the liquid contents of the tank.

6. The method of stopping a vleak in the porous insulating lining of ametallic walled tank from the outside which tank contains a cold boilingliquid, such for example as methane, which consists in making a hole inthe metal wall at the point where the leak has permitted the liquidmethane to contact and chill the tank wall, forcing into the liningthrough the hole under pressure a sealing liquid, the freezing point ofwhich is above the temperature of the liquid contents of the tank.

7. The method of stopping a leak in the porous insulating lining of ametallic Walled tank from the outside which tank contains a cold boilingliquid, such for example as methane, which consists in making a hole in`the metal wall vat the point where the leak has permitted the liquidmethane to contact and chill the tank wall, forcing into the liningthrough the hole under pressure carbon dioxide in gaseous phase, thefreezing point of which is above the temperature of the liquid contentsof the tank, continuing the introduction of the carbon dioxide until ithas penetrated the pores of the lining about the leak, has filled theleak and formed a solid, Dry Ice plug closing the leak.

References Cited in the le of this patent UNITED STATES PATENTS 331,658Sooysmith Dec. l, 1885 908,016 Lake Dec. 29, 1908 2,190,367 Mead Feb.13, 1940 2,476,601 Harper July 17, 1949 2,646,707 Notz July 28, 1953FOREIGN PATENTS 1,006,160 France Jan. 16, 1952

7. THE METHOD OF STOPPING A LEAK IN THE POROUS INSULATING LINING OF AMETALLIC WALLED TANK FROM THE OUTSIDE WHICH TANK CONTAINS A COLD BOILINGLIQUID, SUCH FOR EXAMPLE AS METHANE, WHICH CONSISTS IN MAKING A HOLE INTHE METAL WALL AT THE POINT WHERE THE LEAK HAS PERMITTED THE LIQUIDMETHANE TO CONTACT AND CHILL THE TANK WALL, FORCING INTO THE LININGTHROUGH THE HOLE UNDER PRESSURE CARBON DIOXIDE IN GASEOUS PHASE, THEFREEZING POINT OF WHICH IS ABOVE THE TEMPERATURE OF THE LIQUID CONTENTSOF THE TANK, CONTINUING THE INTRODUCTION OF THE CARBON DIOXIDE UNTIL ITHAS PENETRATED THE PORES OF THE LINING ABOUT THE LEAK, HAS FILLED THELEAK AND FORMED A SOLID, DRY ICE PLUG CLOSING THE LEAK.